The present invention relates to methods of forming selected aluminum halohydrates and to the aluminum halohydrates formed thereby.
The present invention relates more particularly to the methods of forming aluminum iodohydrate, aluminum chlorohydrate, aluminum bromohydrate, and aluminum fluorohydrate.
Generally, aluminum halohydrates have found substantial commercial usages in a wide variety of fields, including use as an active ingredient in body deodorants, tawing salts, and for the impregnation of textiles to impart water repelling properties. In addition, aluminum halohydrates are also used for the preparation of absorption agents or catalytically active substances. Many other commercial uses for the chemicals are well known.
Prior art methods for preparing aluminum halohydrates often include the step of reacting an aluminum halide salt, such as aluminum fluoride, aluminum chloride, aluminum bromide or aluminum iodide with water and metallic aluminum. The process described in the U.S. Pat. No. 3,476,509 includes the use of a water soluble thallium compound with a pH of between 2.5 and 4.4 at an elevated temperature in the order of 70.degree. C. to 105.degree. C. The aluminum hydrate formed from an aluminum halide usually shows traces of the aluminum halide. This has been recognized to be a very serious problem especially for aluminum chlorohydrate when used as an antiperspirant because the aluminum chloride hydrolyzes to hydrochloric acid and results in severe skin irritation. The presence of the aluminum halide also tends to make the aluminum halohydrates hygroscopic.
The article entitled, "Basic Aluminium Compounds" by Hideo Tanabe in The American Perfumer and Cosmetics, Vol. 77, August 1962 pages 25-30 provides a review of known methods for preparing aluminum halohydrates. On page 26, Tanabe presents four methods by way of equations (5), (6), (7), and (8). The four methods are briefly given herein for reference:
1. More than an equivalent amount of metallic aluminum is reacted with an acid, or metallic aluminum is reacted with an aluminum salt with a catalyst of mercury, iron, or copper;
2. More than an equivalent amount of aluminum hydroxide is reacted with an acid;
3. An alkali is added to an aluminum salt solution; and
4. An aqueous solution of an aluminum halide is passed through an anion exchange resin.
On page 26, Tanabe presents the general formula Al.sub.2.sub.+n OH.sub.3n X.sub.6 and indicates that when "n" is large, the solution is slightly turbid but can be made clear by filtration with carbon powder. Tanabe continues with an analysis of the aluminum chlorohydrate and states that each of the four reactions results in a basic aluminum ion which condenses gradually into a polynuclear ion and this condensation is influenced by various conditions such as temperature, time and the the value of "n". Thus, the aluminum chlorohydrate reported by Tanabe appears to show instability with both temperature and time. An earlier Tanable article in Pharm. Soc. Japan, 75 page 868 (1955) is directed to the study of these instabilities.
Another earlier article by Tanabe, in Pharm. Soc. Japan, 74, page 868 (1954) states explicitly that the properties of aluminum chlorohydrate varies with the method of preparation.